I observed that turbulence have tendency to grow even after passing through the object. with that i make an analysis which accurracy i doubt and so I post it here for clarification. here is my analysis: "When a flow was redirected there will be a force that push the object with the direction of the flow and according to Newton’s third law, the flow will be pushed with the same but opposite force thus creating a flow with high energy. A high energy flow will tend to release its energy and it is done by creating a very turbulent movement which create turbulence and the vigorousness of the turbulence will be related with the energy released. When the energy releases are low, only laminar flow pattern will be formed. However, the releases of the energy are not immediate. It increases with time and the discharge will keep increasing until there the energy is below the minimum energy when the turbulence will decay to release the rest of the energy." ps:I am still with my old physics project in https://www.physicsforums.com/showthread.php?t=121164 and it is nothing about reynold number or drag anymore. thanks in advance Arian.